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<div class="refentry">
<a name="GSettingsBackend"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="GSettingsBackend.top_of_page"></a>GSettingsBackend</span></h2>
<p>GSettingsBackend — Interface for settings backend implementations</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="GSettingsBackend.functions"></a><h2>Functions</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="returnvalue">GSettingsBackend</span></a> *
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-settings-backend-get-default" title="g_settings_backend_get_default ()">g_settings_backend_get_default</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-settings-backend-changed" title="g_settings_backend_changed ()">g_settings_backend_changed</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-settings-backend-path-changed" title="g_settings_backend_path_changed ()">g_settings_backend_path_changed</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-settings-backend-keys-changed" title="g_settings_backend_keys_changed ()">g_settings_backend_keys_changed</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-settings-backend-path-writable-changed" title="g_settings_backend_path_writable_changed ()">g_settings_backend_path_writable_changed</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-settings-backend-writable-changed" title="g_settings_backend_writable_changed ()">g_settings_backend_writable_changed</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-settings-backend-changed-tree" title="g_settings_backend_changed_tree ()">g_settings_backend_changed_tree</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-settings-backend-flatten-tree" title="g_settings_backend_flatten_tree ()">g_settings_backend_flatten_tree</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="returnvalue">GSettingsBackend</span></a> *
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-keyfile-settings-backend-new" title="g_keyfile_settings_backend_new ()">g_keyfile_settings_backend_new</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="returnvalue">GSettingsBackend</span></a> *
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-memory-settings-backend-new" title="g_memory_settings_backend_new ()">g_memory_settings_backend_new</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="returnvalue">GSettingsBackend</span></a> *
</td>
<td class="function_name">
<a class="link" href="GSettingsBackend.html#g-null-settings-backend-new" title="g_null_settings_backend_new ()">g_null_settings_backend_new</a> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="GSettingsBackend.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody>
<tr>
<td class="datatype_keyword"> </td>
<td class="function_name"><a class="link" href="GSettingsBackend.html#GSettingsBackend-struct" title="GSettingsBackend">GSettingsBackend</a></td>
</tr>
<tr>
<td class="datatype_keyword">struct</td>
<td class="function_name"><a class="link" href="GSettingsBackend.html#GSettingsBackendClass" title="struct GSettingsBackendClass">GSettingsBackendClass</a></td>
</tr>
<tr>
<td class="define_keyword">#define</td>
<td class="function_name"><a class="link" href="GSettingsBackend.html#G-SETTINGS-BACKEND-EXTENSION-POINT-NAME:CAPS" title="G_SETTINGS_BACKEND_EXTENSION_POINT_NAME">G_SETTINGS_BACKEND_EXTENSION_POINT_NAME</a></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="GSettingsBackend.object-hierarchy"></a><h2>Object Hierarchy</h2>
<pre class="screen">    <a href="https://developer.gnome.org/gobject/unstable/gobject-The-Base-Object-Type.html#GObject">GObject</a>
    <span class="lineart">╰──</span> GSettingsBackend
</pre>
</div>
<div class="refsect1">
<a name="GSettingsBackend.includes"></a><h2>Includes</h2>
<pre class="synopsis">#include &lt;gio/gsettingsbackend.h&gt;
</pre>
</div>
<div class="refsect1">
<a name="GSettingsBackend.description"></a><h2>Description</h2>
<p>The <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> interface defines a generic interface for
non-strictly-typed data that is stored in a hierarchy. To implement
an alternative storage backend for <a class="link" href="GSettings.html" title="GSettings"><span class="type">GSettings</span></a>, you need to implement
the <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> interface and then make it implement the
extension point <a class="link" href="GSettingsBackend.html#G-SETTINGS-BACKEND-EXTENSION-POINT-NAME:CAPS" title="G_SETTINGS_BACKEND_EXTENSION_POINT_NAME"><span class="type">G_SETTINGS_BACKEND_EXTENSION_POINT_NAME</span></a>.</p>
<p>The interface defines methods for reading and writing values, a
method for determining if writing of certain values will fail
(lockdown) and a change notification mechanism.</p>
<p>The semantics of the interface are very precisely defined and
implementations must carefully adhere to the expectations of
callers that are documented on each of the interface methods.</p>
<p>Some of the GSettingsBackend functions accept or return a <a href="https://developer.gnome.org/glib/unstable/glib-Balanced-Binary-Trees.html#GTree"><span class="type">GTree</span></a>.
These trees always have strings as keys and <a href="https://developer.gnome.org/glib/unstable/glib-GVariant.html#GVariant"><span class="type">GVariant</span></a> as values.
<code class="function">g_settings_backend_create_tree()</code> is a convenience function to create
suitable trees.</p>
<p>The GSettingsBackend API is exported to allow third-party
implementations, but does not carry the same stability guarantees
as the public GIO API. For this reason, you have to define the
C preprocessor symbol <code class="literal">G_SETTINGS_ENABLE_BACKEND</code> before including
<code class="literal">gio/gsettingsbackend.h</code>.</p>
</div>
<div class="refsect1">
<a name="GSettingsBackend.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="g-settings-backend-get-default"></a><h3>g_settings_backend_get_default ()</h3>
<pre class="programlisting"><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="returnvalue">GSettingsBackend</span></a> *
g_settings_backend_get_default (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>Returns the default <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a>. It is possible to override
the default by setting the <code class="literal">GSETTINGS_BACKEND</code> environment variable
to the name of a settings backend.</p>
<p>The user gets a reference to the backend.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.2.6"></a><h4>Returns</h4>
<p> the default <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a>. </p>
<p><span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span></p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-28.html#api-index-2.28">2.28</a></p>
</div>
<hr>
<div class="refsect2">
<a name="g-settings-backend-changed"></a><h3>g_settings_backend_changed ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_settings_backend_changed (<em class="parameter"><code><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> *backend</code></em>,
                            <em class="parameter"><code>const <a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *key</code></em>,
                            <em class="parameter"><code><a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> origin_tag</code></em>);</pre>
<p>Signals that a single key has possibly changed.  Backend
implementations should call this if a key has possibly changed its
value.</p>
<p><em class="parameter"><code>key</code></em>
 must be a valid key (ie starting with a slash, not containing
'//', and not ending with a slash).</p>
<p>The implementation must call this function during any call to
<code class="function">g_settings_backend_write()</code>, before the call returns (except in the
case that no keys are actually changed and it cares to detect this
fact).  It may not rely on the existence of a mainloop for
dispatching the signal later.</p>
<p>The implementation may call this function at any other time it likes
in response to other events (such as changes occurring outside of the
program).  These calls may originate from a mainloop or may originate
in response to any other action (including from calls to
<code class="function">g_settings_backend_write()</code>).</p>
<p>In the case that this call is in response to a call to
<code class="function">g_settings_backend_write()</code> then <em class="parameter"><code>origin_tag</code></em>
 must be set to the same
value that was passed to that call.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.3.9"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>backend</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> implementation</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>key</p></td>
<td class="parameter_description"><p>the name of the key</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>origin_tag</p></td>
<td class="parameter_description"><p>the origin tag</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-26.html#api-index-2.26">2.26</a></p>
</div>
<hr>
<div class="refsect2">
<a name="g-settings-backend-path-changed"></a><h3>g_settings_backend_path_changed ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_settings_backend_path_changed (<em class="parameter"><code><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> *backend</code></em>,
                                 <em class="parameter"><code>const <a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *path</code></em>,
                                 <em class="parameter"><code><a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> origin_tag</code></em>);</pre>
<p>Signals that all keys below a given path may have possibly changed.
Backend implementations should call this if an entire path of keys
have possibly changed their values.</p>
<p><em class="parameter"><code>path</code></em>
 must be a valid path (ie starting and ending with a slash and
not containing '//').</p>
<p>The meaning of this signal is that any of the key which has a name
starting with <em class="parameter"><code>path</code></em>
 may have changed.</p>
<p>The same rules for when notifications must occur apply as per
<a class="link" href="GSettingsBackend.html#g-settings-backend-changed" title="g_settings_backend_changed ()"><code class="function">g_settings_backend_changed()</code></a>.  This call might be an appropriate
reasponse to a 'reset' call but implementations are also free to
explicitly list the keys that were affected by that call if they can
easily do so.</p>
<p>For efficiency reasons, the implementation should strive for <em class="parameter"><code>path</code></em>
 to
be as long as possible (ie: the longest common prefix of all of the
keys that were changed) but this is not strictly required.  As an
example, if this function is called with the path of "/" then every
single key in the application will be notified of a possible change.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.4.9"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>backend</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> implementation</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>path</p></td>
<td class="parameter_description"><p>the path containing the changes</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>origin_tag</p></td>
<td class="parameter_description"><p>the origin tag</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-26.html#api-index-2.26">2.26</a></p>
</div>
<hr>
<div class="refsect2">
<a name="g-settings-backend-keys-changed"></a><h3>g_settings_backend_keys_changed ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_settings_backend_keys_changed (<em class="parameter"><code><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> *backend</code></em>,
                                 <em class="parameter"><code>const <a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *path</code></em>,
                                 <em class="parameter"><code><a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> const * const *items</code></em>,
                                 <em class="parameter"><code><a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> origin_tag</code></em>);</pre>
<p>Signals that a list of keys have possibly changed.  Backend
implementations should call this if keys have possibly changed their
values.</p>
<p><em class="parameter"><code>path</code></em>
 must be a valid path (ie starting and ending with a slash and
not containing '//').  Each string in <em class="parameter"><code>items</code></em>
 must form a valid key
name when <em class="parameter"><code>path</code></em>
 is prefixed to it (ie: each item must not start or
end with '/' and must not contain '//').</p>
<p>The meaning of this signal is that any of the key names resulting
from the contatenation of <em class="parameter"><code>path</code></em>
 with each item in <em class="parameter"><code>items</code></em>
 may have
changed.</p>
<p>The same rules for when notifications must occur apply as per
<a class="link" href="GSettingsBackend.html#g-settings-backend-changed" title="g_settings_backend_changed ()"><code class="function">g_settings_backend_changed()</code></a>.  These two calls can be used
interchangeably if exactly one item has changed (although in that
case <a class="link" href="GSettingsBackend.html#g-settings-backend-changed" title="g_settings_backend_changed ()"><code class="function">g_settings_backend_changed()</code></a> is definitely preferred).</p>
<p>For efficiency reasons, the implementation should strive for <em class="parameter"><code>path</code></em>
 to
be as long as possible (ie: the longest common prefix of all of the
keys that were changed) but this is not strictly required.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.5.9"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>backend</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> implementation</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>path</p></td>
<td class="parameter_description"><p>the path containing the changes</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>items</p></td>
<td class="parameter_description"><p> the <a href="https://developer.gnome.org/glib/unstable/glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>-terminated list of changed keys. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter points to an array of items."><span class="acronym">array</span></acronym> zero-terminated=1]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>origin_tag</p></td>
<td class="parameter_description"><p>the origin tag</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-26.html#api-index-2.26">2.26</a></p>
</div>
<hr>
<div class="refsect2">
<a name="g-settings-backend-path-writable-changed"></a><h3>g_settings_backend_path_writable_changed ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_settings_backend_path_writable_changed
                               (<em class="parameter"><code><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> *backend</code></em>,
                                <em class="parameter"><code>const <a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *path</code></em>);</pre>
<p>Signals that the writability of all keys below a given path may have
changed.</p>
<p>Since GSettings performs no locking operations for itself, this call
will always be made in response to external events.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.6.6"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>backend</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> implementation</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>path</p></td>
<td class="parameter_description"><p>the name of the path</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-26.html#api-index-2.26">2.26</a></p>
</div>
<hr>
<div class="refsect2">
<a name="g-settings-backend-writable-changed"></a><h3>g_settings_backend_writable_changed ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_settings_backend_writable_changed (<em class="parameter"><code><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> *backend</code></em>,
                                     <em class="parameter"><code>const <a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *key</code></em>);</pre>
<p>Signals that the writability of a single key has possibly changed.</p>
<p>Since GSettings performs no locking operations for itself, this call
will always be made in response to external events.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.7.6"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>backend</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> implementation</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>key</p></td>
<td class="parameter_description"><p>the name of the key</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-26.html#api-index-2.26">2.26</a></p>
</div>
<hr>
<div class="refsect2">
<a name="g-settings-backend-changed-tree"></a><h3>g_settings_backend_changed_tree ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_settings_backend_changed_tree (<em class="parameter"><code><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> *backend</code></em>,
                                 <em class="parameter"><code><a href="https://developer.gnome.org/glib/unstable/glib-Balanced-Binary-Trees.html#GTree"><span class="type">GTree</span></a> *tree</code></em>,
                                 <em class="parameter"><code><a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> origin_tag</code></em>);</pre>
<p>This call is a convenience wrapper.  It gets the list of changes from
<em class="parameter"><code>tree</code></em>
, computes the longest common prefix and calls
<a class="link" href="GSettingsBackend.html#g-settings-backend-changed" title="g_settings_backend_changed ()"><code class="function">g_settings_backend_changed()</code></a>.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.8.5"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>backend</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> implementation</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>tree</p></td>
<td class="parameter_description"><p>a <a href="https://developer.gnome.org/glib/unstable/glib-Balanced-Binary-Trees.html#GTree"><span class="type">GTree</span></a> containing the changes</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>origin_tag</p></td>
<td class="parameter_description"><p>the origin tag</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-26.html#api-index-2.26">2.26</a></p>
</div>
<hr>
<div class="refsect2">
<a name="g-settings-backend-flatten-tree"></a><h3>g_settings_backend_flatten_tree ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
g_settings_backend_flatten_tree (<em class="parameter"><code><a href="https://developer.gnome.org/glib/unstable/glib-Balanced-Binary-Trees.html#GTree"><span class="type">GTree</span></a> *tree</code></em>,
                                 <em class="parameter"><code><a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> **path</code></em>,
                                 <em class="parameter"><code>const <a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> ***keys</code></em>,
                                 <em class="parameter"><code><a href="https://developer.gnome.org/glib/unstable/glib-GVariant.html#GVariant"><span class="type">GVariant</span></a> ***values</code></em>);</pre>
<p>Calculate the longest common prefix of all keys in a tree and write
out an array of the key names relative to that prefix and,
optionally, the value to store at each of those keys.</p>
<p>You must free the value returned in <em class="parameter"><code>path</code></em>
, <em class="parameter"><code>keys</code></em>
 and <em class="parameter"><code>values</code></em>
 using
<a href="https://developer.gnome.org/glib/unstable/glib-Memory-Allocation.html#g-free"><code class="function">g_free()</code></a>.  You should not attempt to free or unref the contents of
<em class="parameter"><code>keys</code></em>
 or <em class="parameter"><code>values</code></em>
.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.9.6"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>tree</p></td>
<td class="parameter_description"><p>a <a href="https://developer.gnome.org/glib/unstable/glib-Balanced-Binary-Trees.html#GTree"><span class="type">GTree</span></a> containing the changes</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>path</p></td>
<td class="parameter_description"><p> the location to save the path. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>keys</p></td>
<td class="parameter_description"><p> the
location to save the relative keys. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>][<acronym title="Free data container after the code is done."><span class="acronym">transfer container</span></acronym>][<acronym title="Parameter points to an array of items."><span class="acronym">array</span></acronym> zero-terminated=1]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>values</p></td>
<td class="parameter_description"><p>         the location to save the values, or <a href="https://developer.gnome.org/glib/unstable/glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>][<acronym title="NULL is OK, both for passing and for returning."><span class="acronym">allow-none</span></acronym>][<acronym title="Free data container after the code is done."><span class="acronym">transfer container</span></acronym>][<acronym title="Parameter points to an array of items."><span class="acronym">array</span></acronym> zero-terminated=1]</span></td>
</tr>
</tbody>
</table></div>
</div>
<p class="since">Since: <a class="link" href="api-index-2-26.html#api-index-2.26">2.26</a></p>
</div>
<hr>
<div class="refsect2">
<a name="g-keyfile-settings-backend-new"></a><h3>g_keyfile_settings_backend_new ()</h3>
<pre class="programlisting"><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="returnvalue">GSettingsBackend</span></a> *
g_keyfile_settings_backend_new (<em class="parameter"><code>const <a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *filename</code></em>,
                                <em class="parameter"><code>const <a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *root_path</code></em>,
                                <em class="parameter"><code>const <a href="https://developer.gnome.org/glib/unstable/glib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *root_group</code></em>);</pre>
<p>Creates a keyfile-backed <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a>.</p>
<p>The filename of the keyfile to use is given by <em class="parameter"><code>filename</code></em>
.</p>
<p>All settings read to or written from the backend must fall under the
path given in <em class="parameter"><code>root_path</code></em>
 (which must start and end with a slash and
not contain two consecutive slashes).  <em class="parameter"><code>root_path</code></em>
 may be "/".</p>
<p>If <em class="parameter"><code>root_group</code></em>
 is non-<a href="https://developer.gnome.org/glib/unstable/glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> then it specifies the name of the keyfile
group used for keys that are written directly below <em class="parameter"><code>root_path</code></em>
.  For
example, if <em class="parameter"><code>root_path</code></em>
 is "/apps/example/" and <em class="parameter"><code>root_group</code></em>
 is
"toplevel", then settings the key "/apps/example/enabled" to a value
of <a href="https://developer.gnome.org/glib/unstable/glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> will cause the following to appear in the keyfile:</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1
2</pre></td>
        <td class="listing_code"><pre class="programlisting"><span class="gtkdoc opt">[</span>toplevel<span class="gtkdoc opt">]</span>
enabled<span class="gtkdoc opt">=</span><span class="keyword">true</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p></p>
<p>If <em class="parameter"><code>root_group</code></em>
 is <a href="https://developer.gnome.org/glib/unstable/glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> then it is not permitted to store keys
directly below the <em class="parameter"><code>root_path</code></em>
.</p>
<p>For keys not stored directly below <em class="parameter"><code>root_path</code></em>
 (ie: in a sub-path),
the name of the subpath (with the final slash stripped) is used as
the name of the keyfile group.  To continue the example, if
"/apps/example/profiles/default/font-size" were set to
12 then the following would appear in the keyfile:</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1
2</pre></td>
        <td class="listing_code"><pre class="programlisting"><span class="gtkdoc opt">[</span>profiles<span class="gtkdoc opt">/</span><span class="keyword">default</span><span class="gtkdoc opt">]</span>
font<span class="gtkdoc opt">-</span>size<span class="gtkdoc opt">=</span><span class="number">12</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p></p>
<p>The backend will refuse writes (and return writability as being
<a href="https://developer.gnome.org/glib/unstable/glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a>) for keys outside of <em class="parameter"><code>root_path</code></em>
 and, in the event that
<em class="parameter"><code>root_group</code></em>
 is <a href="https://developer.gnome.org/glib/unstable/glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>, also for keys directly under <em class="parameter"><code>root_path</code></em>
.
Writes will also be refused if the backend detects that it has the
inability to rewrite the keyfile (ie: the containing directory is not
writable).</p>
<p>There is no checking done for your key namespace clashing with the
syntax of the key file format.  For example, if you have '[' or ']'
characters in your path names or '=' in your key names you may be in
trouble.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.10.16"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>filename</p></td>
<td class="parameter_description"><p>the filename of the keyfile</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>root_path</p></td>
<td class="parameter_description"><p>the path under which all settings keys appear</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>root_group</p></td>
<td class="parameter_description"><p> the group name corresponding to
<em class="parameter"><code>root_path</code></em>
, or <a href="https://developer.gnome.org/glib/unstable/glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="NULL is OK, both for passing and for returning."><span class="acronym">allow-none</span></acronym>]</span></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.4.19.3.8.10.17"></a><h4>Returns</h4>
<p> a keyfile-backed <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a>. </p>
<p><span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span></p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="g-memory-settings-backend-new"></a><h3>g_memory_settings_backend_new ()</h3>
<pre class="programlisting"><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="returnvalue">GSettingsBackend</span></a> *
g_memory_settings_backend_new (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>Creates a memory-backed <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a>.</p>
<p>This backend allows changes to settings, but does not write them
to any backing storage, so the next time you run your application,
the memory backend will start out with the default values again.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.11.6"></a><h4>Returns</h4>
<p> a newly created <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a>. </p>
<p><span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span></p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-28.html#api-index-2.28">2.28</a></p>
</div>
<hr>
<div class="refsect2">
<a name="g-null-settings-backend-new"></a><h3>g_null_settings_backend_new ()</h3>
<pre class="programlisting"><a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="returnvalue">GSettingsBackend</span></a> *
g_null_settings_backend_new (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>Creates a readonly <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a>.</p>
<p>This backend does not allow changes to settings, so all settings
will always have their default values.</p>
<div class="refsect3">
<a name="id-1.4.19.3.8.12.6"></a><h4>Returns</h4>
<p> a newly created <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a>. </p>
<p><span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span></p>
</div>
<p class="since">Since: <a class="link" href="api-index-2-28.html#api-index-2.28">2.28</a></p>
</div>
</div>
<div class="refsect1">
<a name="GSettingsBackend.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="GSettingsBackend-struct"></a><h3>GSettingsBackend</h3>
<pre class="programlisting">typedef struct _GSettingsBackend GSettingsBackend;</pre>
<p>An implementation of a settings storage repository.</p>
</div>
<hr>
<div class="refsect2">
<a name="GSettingsBackendClass"></a><h3>struct GSettingsBackendClass</h3>
<pre class="programlisting">struct GSettingsBackendClass {
  GObjectClass parent_class;

  GVariant *    (*read)             (GSettingsBackend    *backend,
                                     const gchar         *key,
                                     const GVariantType  *expected_type,
                                     gboolean             default_value);

  gboolean      (*get_writable)     (GSettingsBackend    *backend,
                                     const gchar         *key);

  gboolean      (*write)            (GSettingsBackend    *backend,
                                     const gchar         *key,
                                     GVariant            *value,
                                     gpointer             origin_tag);
  gboolean      (*write_tree)       (GSettingsBackend    *backend,
                                     GTree               *tree,
                                     gpointer             origin_tag);
  void          (*reset)            (GSettingsBackend    *backend,
                                     const gchar         *key,
                                     gpointer             origin_tag);

  void          (*subscribe)        (GSettingsBackend    *backend,
                                     const gchar         *name);
  void          (*unsubscribe)      (GSettingsBackend    *backend,
                                     const gchar         *name);
  void          (*sync)             (GSettingsBackend    *backend);

  GPermission * (*get_permission)   (GSettingsBackend    *backend,
                                     const gchar         *path);

  GVariant *    (*read_user_value)  (GSettingsBackend    *backend,
                                     const gchar         *key,
                                     const GVariantType  *expected_type);
};
</pre>
<p>Class structure for <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a>.</p>
<div class="refsect3">
<a name="id-1.4.19.3.9.3.5"></a><h4>Members</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="300px" class="struct_members_name">
<col class="struct_members_description">
<col width="200px" class="struct_members_annotations">
</colgroup>
<tbody>
<tr>
<td class="struct_member_name"><p><a href="https://developer.gnome.org/gobject/unstable/gobject-The-Base-Object-Type.html#GObjectClass"><span class="type">GObjectClass</span></a> <em class="structfield"><code><a name="GSettingsBackendClass.parent-class"></a>parent_class</code></em>;</p></td>
<td> </td>
<td> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.read"></a>read</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to read a key's value</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.get-writable"></a>get_writable</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to get if a key is writable</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.write"></a>write</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to change key's value</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.write-tree"></a>write_tree</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to change a tree of keys</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.reset"></a>reset</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to reset state</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.subscribe"></a>subscribe</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to subscribe to key changes</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.unsubscribe"></a>unsubscribe</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to unsubscribe to key changes</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.sync"></a>sync</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to sync state</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.get-permission"></a>get_permission</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to get permission of a key</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSettingsBackendClass.read-user-value"></a>read_user_value</code></em> ()</p></td>
<td class="struct_member_description"><p>virtual method to read user's key value</p></td>
<td class="struct_member_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="G-SETTINGS-BACKEND-EXTENSION-POINT-NAME:CAPS"></a><h3>G_SETTINGS_BACKEND_EXTENSION_POINT_NAME</h3>
<pre class="programlisting">#define G_SETTINGS_BACKEND_EXTENSION_POINT_NAME "gsettings-backend"
</pre>
<p>Extension point for <a class="link" href="GSettingsBackend.html" title="GSettingsBackend"><span class="type">GSettingsBackend</span></a> functionality.</p>
</div>
</div>
<div class="refsect1">
<a name="GSettingsBackend.see-also"></a><h2>See Also</h2>
<p><a class="link" href="GSettings.html" title="GSettings"><span class="type">GSettings</span></a>, <a class="link" href="gio-Extension-Points.html#GIOExtensionPoint" title="GIOExtensionPoint"><span class="type">GIOExtensionPoint</span></a></p>
</div>
</div>
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